Table 1.

Overview of included studies.

Reference	Design	Patients		Etiology		tDCS protocol	Sitimulation target	Adverse effect
Martens et al. (8)	Randomized, sham-controlled crossover study	MCS PVS	29 16	TBI Non-TBI	24 22	1 session, 20 minus 4 mA tDCS 1 session, 20 minus sham tDCS 48 hours washout	Bilateral frontoparietal	None
Wu et al. (9)	Randomized, sham-controlled parallel study	MCS PVS	7 8	TBI Non-TBI	10 5	10 session, 20 minus 2 mA tDCS 10 session, 20 minus sham tDCS	Left/right DLPFC	None
Carriere et al. (5)	Randomized, sham-controlled crossover study	MCS	10	TBI Non-TBI	8 2	1 session, 20 minus 2 mA tDCS 1 session, 20 minus sham tDCS 48 hours washout	Left DLPFC	None
Martens et al. (19)	Randomized, sham-controlled crossover study	MCS PVS	21 6	TBI Non-TBI	15 12	10 session, 20 minus 2 mA tDCS 10 session, 20 minus sham tDCS 8 weeks washout	Left DLPFC	Skin redness in 10 patients, Sleppiness in 3 patients, Epileptic seizure in 1 patients
Martens et al. (7)	Randomized, sham-controlled crossover study	MCS PVS	6 4	TBI Non-TBI	5 5	1 session, 20 minus 2 mA tDCS 1 session, 20 minus sham tDCS 24 hours washout	Left/right M1	None
Zhang et al. (10)	Randomized, sham-controlled parallel study	MCS PVS	15 11	TBI Non-TBI	14 12	20 session, 20 minus 2 mA tDCS 20 session, 20 minus sham tDCS	Left DLPFC	None
Estraneo et al. (6)	Randomized, sham-controlled crossover study	MCS PVS	6 7	TBI Non-TBI	1 12	5 session, 20 minus 2 mA tDCS 5 session, 20 minus sham tDCS 1 week washout	Left DLPFC	None
Huang et al. (18)	Randomized, sham-controlled crossover study	MCS	33	TBI Non-TBI	13 20	5 session, 20 minus 2 mA tDCS 5 session, 20 minus sham tDCS 5 days washout	Posterior parietal cortex	None

Individual patient data were obtained for all trials.

tDCS, transcranial direct current stimulation; MCS, minimally conscious state; PVS, persistent vegetative state; TBI, traumatic brain injury; DLPFC, dorsolateral prefrontal cortex; M1, primary motor cortex.